The aims of this renewal application will continue to investigate how changes in elastin deposition and assembly influence blood vessel development and cardiovascular function. We also seek to understand how elastin mutations that alter elastic fiber assembly lead to vascular disease. During the previous funding period we showed a strong correlation between the rise in blood pressure and the increase in elastin production during development. Blood pressure and elastin synthesis increase coordinately through the fetal and postnatal period and blood pressure stabilizes when elastin production ends between P21-P30. Although there is no generally accepted explanation for what directs the changes in hemodynamics and SMC matrix production, wall stress is considered to be the major player. The ECM, in contrast, is regarded as a static component that contributes to the mechanical properties of the wall but otherwise has no say in the matter. We propose that H2O2 generated during elastic fiber formation acts as a signaling molecule to directly influence cellular differentiation and cardiac function as the cardiovascular system matures. Instead of the traditional view that alterations in blood pressure direct matrix production exclusively through signals associated with wall stress, our model suggests that reactive oxygen species (ROS) signals generated during active matrix synthesis and maturation influence adjustments in blood pressure and cell differentiation through direct signaling or by modulating mechanical signaling pathways. Because increases in blood pressure can only occur to the extent that they can be accommodated by the vessel wall, feedback signals from the structural components responsible for vessel integrity are an efficient way to signal the cardiovascular system that the wall has achieved the required strength and appropriate mechanical properties to accommodate changes in flow and pressure. Coupling signaling to crosslinking of elastin provides information about both elastin synthesis and, most importantly, the maturation state of elastin. Thus, the underlying hypothesis of this application is that ROS generated during elastin crosslinking provide a regulatory signal that influences smooth muscle cell differentiation and cardiovascular physiology. We also propose that elastin-derived ROS influence the angiotensin signaling pathway and that this pathway is responsible for the adaptive remodeling that occurs in elastin insufficiency. Our specific aims are: 1) To explore a novel signaling mechanism mediated by reactive oxygen species generated during elastin crosslinking. 2) To determine how the renin-angiotensin system directs vascular remodeling in late gestation elastin insufficiency. 3) To explore treatment strategies designed to rescue elastin insufficiency (SVAS).